Automotive ECU

Automotive ECU

An electronic control system (ECU) is an embedded system that controls one or more vehicle systems – from powertrain to infotainment and in modern vehicles, all systems related to driver assistance and automated driving, from sensors to actuators. ASIL D is mandatory with most domain controllers and clocks play a significant role in supporting functional safety requirements.

SiTime MEMS timing solutions provide the performance needed for automotive ECUs as E/E architectures increasingly rely on high-speed interfaces. SiTime clocks offer high accuracy, better stability over temperature, resilience to shock and vibration, and low jitter.

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SiTime MEMS Timing Benefits

Complete MEMS clock tree

Spread spectrum oscillators

Low jitter differential oscillators

32.768-kHz XOs and TCXOs

Precision TCXOs

Most robust in real world conditions

150 fs rms jitter, excellent PSNR

Resistant to shock and vibration

Stable over wide temperature

2.2 billion hours MTBF

Integrated MEMS, easy to use

No quartz reliability issues

Reliable startup in cold temp

No cover or shielding needed

Short lead time for any frequency

Automotive ECU Block Diagram

Automotive ECU block diagramsitime.com32.768 kHz XO SiT1881XO SiT8924TCXO SiT5386Differential XO SiT9396Differential XO SiT9396Differential XO SiT9396

The transition from distributed architecture in vehicles to domain architecture has a significant impact on timing. With domain architecture, the use of higher-speed interfaces places a greater need on low jitter clocks. As ECU complexity has increased, more clocks are needed. Functional safety is an integral part of today's automotive systems. ASIL D is mandatory with most domain controllers, and clocks play a significant role in supporting functional safety requirements.​

MEMS Timing Solutions for Automotive ECU

Devices Key Features Key Values
Single-ended Oscillator
SiT8924  1 to 110 MHz
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  • Up to -55°C to +125°C
  • ±20 ppm stability
  • 2016, 2520, 3225 packages
  • High reliability
  • Extended temperature range
  • Small footprint
Single-ended Oscillator
SiT9025  1 to 110 MHz
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  • Up to -55°C to +125°C
  • Spread spectrum
  • Configurable rise / fall times
  • 2016, 2520, 3225 packages
  • High reliability
  • Extended temperature range
  • EMI Reduction
Differential Oscillators
SiT9396  1 to 220 MHz
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SiT9397  220 to 920 MHz
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  • Low jitter: < 150 fs RMS [1]
  • ±30, ±50 ppm stability over -40 to +125°C
  • LVPECL, LVDS, HCSL, Low-power HCSL, FlexSwing™
  • 2016, 2520, 3225 packages
  • High reliability
  • Low jitter
  • Enables interfaces with demanding jitter requirements, such as PCI-Express and 10 GB Ethernet
Super-TCXOs
SiT5386  1 to 60 MHz
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SiT5387  60 to 220 MHz
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  • ±0.1, ±0.2, ±0.25 ppm stability over -40 to +125°C
  • ±1 ppb/°C frequency slope
  • Low jitter: 0.31 ps RMS [1]
  • Optional voltage or digital frequency control
  • High accuracy
  • Excellent frequency stability with fast temp gradients
  • No GNSS signal loss or V2X disconnect due to micro-jumps
32.768 kHz Oscillator
  • ±20, ±50, ±100 ppm stability over -40 to +125°C
  • 1.14 to 3.63 V supply
  • < 490 nA consumption
  • 1.2 x 1.1 mm
  • < 115 ms startup time
  • Excellent stability
  • Low power
  • Small footprint
  • Faster start-up time 32.768 kHz tuning-fork crystals
  • High reliability for functional safety applications

1 12 kHz to 20 MHz integration range

SiTime Advantages

SiTime devices offer the following benefits over quartz crystals, which are particularly important in automotive.

  • 50x better reliability. Apart from reducing the amount of field failures, the better reliability translates into a lower FIT rate. This provides better hardware safety metrics in an FMEDA, the quantitative analysis required as part of a functional safety assessment.
  • 100x better resilience to shock, vibration and electromagnetic interference, due to the smaller size (0.4 x 0.4 mm) and lower mass of MEMS resonators compared to crystals. When not causing a permanent damage to the crystal, shock and vibration can induce jitter in a crystal oscillator. As seen previously, jitter can be detrimental to the bit error rate of a high-speed link. Better resilience of SiTime oscillators ensures a low error rate regardless of operating conditions.
  • Better frequency accuracy, 10x lower aging, and excellent stability over temperature – down to ±20 ppm (XO devices) over -40 to +125°C and ±0.1 ppm (TCXO devices) over -40 to +105°C.

MEMS Timing Outperforms Quartz

Higher Quality

Higher Reliability

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 SiTime – Higher Quality
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SiTime timing devices are up to 50x more reliable than legacy quartz

Tighter Stability

Better EMI Reduction

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SiTime – Tighter Stability
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SiTime – Better EMI Reduction

Immune to Vibration

Better Noise Rejection

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SiTime – Immune to Vibration
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SiTime – Better Noise Rejection
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